Telephone calls are often placed across networks for different telephone companies or service providers. Call origination is the initiation, by a calling party, of a telephone call in a provider network. Call termination is the routing of the telephone call from the provider network to a called party in the same or another provider network. The called party is usually identified by a public user identifier (ID), such as a telephone number.
Third generation partnership project (3GPP) Internet protocol (IP) multimedia system (IMS) currently supports two states for a subscriber provisioned within a home subscriber server (HSS). These states are: barred and not barred. If a subscriber (public identity) is barred (e.g., because of payment delinquency or becoming inactive), the IMS may require that the IMS core (e.g., serving call state control function (S-CSCF) devices) prevent that public identity from being used in any IMS communication except for registration and re-registrations. However, non-emergency access may be required in the barred state. Current applications use application servers to maintain awareness of subscription state, to provide non-emergency access and to restrict services, etc.